Orthogonal Frequency Division Multiplexing (OFDM) is an effective way to mitigate the multipath spread of the wireless channels by a simple equalization. Due to its robustness against the multipath spread of the channel and its high spectral efficiency, it has been widely adopted in different wireless standards, for example DVB-T/H, and it is also being considered as the most valuable candidate for future cellular radio systems. Though its advantages, the reception quality of OFDM systems is hampered by the intercarrier interference (ICI) due to the Doppler spread of the signal in high mobility scenarios. Mobility induced Doppler spreading distorts the orthogonality among the subcarriers, and results in intercarrier interferences. ICI degrades the reception quality by worsening the demodulation and decreasing the accuracy of the channel estimates. The ICI problem in mobile OFDM systems is a well known and widely studied problem.
The conventional solutions can be grouped under three categories, that means signal processing based ICI cancellation schemes, self ICI cancelling coding schemes, and multiple antenna techniques. Signal processing based ICI cancellation schemes require estimation of the time varying characteristics of the channel to estimate the interference of each subcarrier to its adjacent subcarriers to cancel the ICI, whereas self ICI cancelling coding schemes provide robustness to the mobility at the expense of reduced spectral efficiency. The multiple antenna approaches are based on exploiting antenna diversity and spatial processing to mitigate the ICI. Signal processing based ICI cancellation schemes are quite popular since they do not have any penalty in spectral efficiency or hardware cost with respect to self ICI cancelling coding schemes and multiple antenna solutions, respectively.
Although some Doppler compensation techniques are quite effective in single antenna mobile OFDM receivers, these schemes use the channel information obtained through the channel estimation stage which is also affected adversely by the ICI, thus, their performance is limited by the accuracy of these estimates. As the mobility induced Doppler spreading increases, the ICI power increases affecting also the pilot symbols that will be used for channel estimation stage.